I did a quick test with LUCEE_ENABLE_BUNDLE_DOWNLOAD
set to false
and I get the following errors in my console:
[INFO ] 22.04.2022 16:07:05,480 ERROR [server.application] OSGi->Lucee is missing the Bundle jar, org.lucee.commons.logging:1.2.0, and has been prevented from downloading it. If this jar is not a core jar, it will need to be manually downloaded and placed in the {{lucee-server}}/context/bundles directory.
[INFO ] 22.04.2022 16:07:05,507 ERROR [server.application] OSGi->The OSGi Bundle with name [org.lucee.commons.logging] is not available in version [1.2.0] locally (D:\.Command Box\server\5DFAEA950B8E8D28B92DB9FA2667057F-5.3.9-bundle-download-test\lucee-5.3.9.129-SNAPSHOT\WEB-INF\lucee-server\bundles) or from the update provider (http://release.lucee.org), the following versions are available locally [1.2.0.0000L, 1.2.0.0000L].
That second one is a real gem since it tells me 1.2.0 is not available locally, only to turn around and tell me 1.2.0 IS available locally, not once but twice! 
My deploy log is also chock full of errors like this. Why are these even errors, or being logged at all?
"ERROR","main","04/22/2022","16:07:07","Extension","the extension MySQL (id: 7E673D15-D87C-41A6-8B5F1956528C605F) in version 8.0.19 is already installed;lucee.runtime.exp.ApplicationException: the extension MySQL (id: 7E673D15-D87C-41A6-8B5F1956528C605F) in version 8.0.19 is already installed
at lucee.runtime.config.XMLConfigAdmin.updateRHExtension(XMLConfigAdmin.java:4699)
at lucee.runtime.config.XMLConfigAdmin.updateRHExtension(XMLConfigAdmin.java:4692)
at lucee.runtime.config.XMLConfigAdmin._updateRHExtension(XMLConfigAdmin.java:4674)
at lucee.runtime.config.DeployHandler.deploy(DeployHandler.java:88)
at lucee.runtime.engine.CFMLEngineImpl.<init>(CFMLEngineImpl.java:414)
at lucee.runtime.engine.CFMLEngineImpl.getInstance(CFMLEngineImpl.java:746)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base/java.lang.reflect.Method.invoke(Unknown Source)
at lucee.loader.engine.CFMLEngineFactory.getEngine(CFMLEngineFactory.java:1451)
at lucee.loader.engine.CFMLEngineFactory.initEngine(CFMLEngineFactory.java:384)
at lucee.loader.engine.CFMLEngineFactory.initEngineIfNecessary(CFMLEngineFactory.java:262)
at lucee.loader.engine.CFMLEngineFactory.getInstance(CFMLEngineFactory.java:168)
at lucee.loader.engine.CFMLEngineFactory.getInstance(CFMLEngineFactory.java:202)
at lucee.loader.servlet.LuceeServlet.init(LuceeServlet.java:42)
...
I also see a handful of these errors in my deploy log
"ERROR","main","04/22/2022","16:07:07","Extension","D:\.Command Box\server\5DFAEA950B8E8D28B92DB9FA2667057F-5.3.9-bundle-download-test\lucee-5.3.9.129-SNAPSHOT\WEB-INF\lucee-server\context\extensions\installed\1apdrbs8iaisw.lex (Access is denied);lucee.runtime.exp.NativeException: D:\.Command Box\server\5DFAEA950B8E8D28B92DB9FA2667057F-5.3.9-bundle-download-test\lucee-5.3.9.129-SNAPSHOT\WEB-INF\lucee-server\context\extensions\installed\1apdrbs8iaisw.lex (Access is denied)
at java.base/java.io.FileOutputStream.open0(Native Method)
at java.base/java.io.FileOutputStream.open(Unknown Source)
at java.base/java.io.FileOutputStream.<init>(Unknown Source)
at lucee.commons.io.res.type.file.FileResource.getOutputStream(FileResource.java:264)
at lucee.commons.io.res.type.file.FileResource.copyTo(FileResource.java:116)
at lucee.commons.io.IOUtil.copy(IOUtil.java:140)
at lucee.commons.io.res.util.ResourceUtil.moveTo(ResourceUtil.java:1120)
at lucee.runtime.extension.RHExtension.move(RHExtension.java:251)
at lucee.runtime.extension.RHExtension.init(RHExtension.java:238)
at lucee.runtime.extension.RHExtension.<init>(RHExtension.java:224)
at lucee.runtime.config.XMLConfigAdmin.updateRHExtension(XMLConfigAdmin.java:4684)
at lucee.runtime.config.XMLConfigAdmin._updateRHExtension(XMLConfigAdmin.java:4674)
at lucee.runtime.config.DeployHandler.deploy(DeployHandler.java:88)
at lucee.runtime.engine.CFMLEngineImpl.<init>(CFMLEngineImpl.java:414)
at lucee.runtime.engine.CFMLEngineImpl.getInstance(CFMLEngineImpl.java:746)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base/java.lang.reflect.Method.invoke(Unknown Source)
at lucee.loader.engine.CFMLEngineFactory.getEngine(CFMLEngineFactory.java:1451)
at lucee.loader.engine.CFMLEngineFactory.initEngine(CFMLEngineFactory.java:384)
at lucee.loader.engine.CFMLEngineFactory.initEngineIfNecessary(CFMLEngineFactory.java:262)
at lucee.loader.engine.CFMLEngineFactory.getInstance(CFMLEngineFactory.java:168)
at lucee.loader.engine.CFMLEngineFactory.getInstance(CFMLEngineFactory.java:202)
at lucee.loader.servlet.LuceeServlet.init(LuceeServlet.java:42)
at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:117)
at io.undertow.servlet.core.ManagedServlet$DefaultInstanceStrategy.start(ManagedServlet.java:309)
at io.undertow.servlet.core.ManagedServlet.createServlet(ManagedServlet.java:145)
at io.undertow.servlet.core.DeploymentManagerImpl$2.call(DeploymentManagerImpl.java:588)
at io.undertow.servlet.core.DeploymentManagerImpl$2.call(DeploymentManagerImpl.java:559)
at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:42)
at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
at io.undertow.servlet.core.DeploymentManagerImpl.start(DeploymentManagerImpl.java:601)
at runwar.Server.createServletDeployment(Server.java:1314)
at runwar.Server.startServer(Server.java:485)
at runwar.Start.main(Start.java:50)
Caused by: java.io.FileNotFoundException: D:\.Command Box\server\5DFAEA950B8E8D28B92DB9FA2667057F-5.3.9-bundle-download-test\lucee-5.3.9.129-SNAPSHOT\WEB-INF\lucee-server\context\extensions\installed\1apdrbs8iaisw.lex (Access is denied)
... 37 more
This was just a default server started up on CommandBox in Windows. I’ve made no changes or installed anything custom into it yet.