Subject: Trouble starting Solr on Windows/Ubuntu

I'm trying to follow the Solr Tutorial (

Yesterday, "bin/solr start" worked fine -- I could see the status page on
http://localhost:8993 . I even created a test config server/solr/test1
through the Web interface.

Today, I'm getting an error message when I try to start Solr. This is from
an Ubuntu top-level shell (I previously tried a shell buffer within Emacs
under Ubuntu, which failed). I've rebooted Windows, and it still fails. See
transcript and version info below.

What am I doing wrong? -- and is solr-user the right place to ask newbie
questions like this?
(None of the env variables mentioned in the error message are defined.)

xxx:/mnt/c/solr-8.5.1$ bin/solr status -help

No Solr nodes are running.

xxx:/mnt/c/solr-8.5.1$ bin/solr start
Waiting up to 180 seconds to see Solr running on port 8983 [|]  bin/solr:
line 669:  8456 Aborted                 (core dumped) nohup "$JAVA"
"${SOLR_START_OPTS[@]}" $SOLR_ADDL_ARGS -Dsolr.log.muteconsole
"-XX:OnOutOfMemoryError=$SOLR_TIP/bin/ $SOLR_PORT
$SOLR_LOGS_DIR" -jar start.jar "${SOLR_JETTY_CONFIG[@]}"
 [/]  Still not seeing Solr listening on 8983 after 180 seconds!
tail: cannot open '/mnt/c/solr-8.5.1/server/logs/solr.log' for reading: No
such file or directory

xxx:/mnt/c/solr-8.5.1$ echo foo > /mnt/c/solr-8.5.1/server/logs/solr.log
xxx:/mnt/c/solr-8.5.1$ cat /mnt/c/solr-8.5.1/server/logs/solr.log
foo                   <<< log file is writeable

------------versions ------------

xxx:/mnt/c/solr-8.5.1$ uname -a
Linux DESKTOP-M6LDB7Q 4.4.0-18362-Microsoft #836-Microsoft Mon May 05
16:04:00 PST 2020 x86_64 x86_64 x86_64 GNU/Linux
xxx:/mnt/c/solr-8.5.1$ which java
xxx:/mnt/c/solr-8.5.1$ java -version
openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment (build 11.0.7+10-post-Ubuntu-2ubuntu218.04)
OpenJDK 64-Bit Server VM (build 11.0.7+10-post-Ubuntu-2ubuntu218.04, mixed
mode, sharing)
xxx:/mnt/c/solr-8.5.1$ bin/solr -version