package mysql-server-8.0 8.0.23-0ubuntu0.20.04.1 failed to install/upgrade: installed mysql-server-8.0 package post-installation script subprocess returned error exit status 1

Thanks for taking the time to report this bug and helping to make Ubuntu better. We appreciate the difficulties you are facing, but this appears to be a "regular" (non-security) bug. I have unmarked it as a security issue since this bug does not show evidence of allowing attackers to cross privilege boundaries nor directly cause loss of data/privacy. Please feel free to report any other bugs you may find.

Thank you for taking the time to file a bug report.

Based on the logs you attached to the bug, I can see a few things that caught my attention and are making me wonder whether this is a local configuration issue.

First, from DpkgHistoryLog.txt, I see a bunch of dpkg errors like:

Start-Date: 2021-03-16 10:38:36
Commandline: apt remove phpmyadmin php-mbstring php-zip php-gd php-json php-curl
Remove: php-gd:amd64 (2:7.4+75), php-zip:amd64 (2:7.4+75), phpmyadmin:amd64 (4:4.9.5+dfsg1-2), php-json:amd64 (2:7.4+75), php-curl:amd64 (2:7.4+75), php-mbstring:amd64 (2:7.4+75)
Error: Sub-process /usr/bin/dpkg returned an error code (1)
End-Date: 2021-03-16 10:39:35

Start-Date: 2021-03-17 11:09:11
Commandline: apt install vim
Install: vim-runtime:amd64 (2:8.1.2269-1ubuntu5, automatic), vim:amd64 (2:8.1.2269-1ubuntu5)
Error: Sub-process /usr/bin/dpkg returned an error code (1)
End-Date: 2021-03-17 11:10:20

... and so on.

These are very strange errors, and tell me that dpkg is having trouble doing relatively simple operations such as installing vim, htop, etc.

From DpkgTerminalLog.txt, I see a strange, mangled output which eventually ends with:

dpkg: error processing package phpmyadmin (--configure):
 installed phpmyadmin package post-installation script subprocess returned error exit status 1

This means that phpmyadmin failed to be configured, possibly leaving the package in an inconsistent state. I'm not sure offhand if this failure could also impact mysql-server's installation, but it is possible, especially if we take into account the (cryptic) log that comes right before this part:

Package configuration┌──────┤ Configuring phpmyadmin ├───────┐│ Next step for database installation:...
...
[?1049ldbconfig-common: phpmyadmin configure: aborted.

And then, from Logs.var.log.mysql.error.log.txt I see:

2021-03-23T07:33:44.041940Z 0 [ERROR] [MY-010262] [Server] Can't start server: Bind on TCP/IP port: Address already in use
2021-03-23T07:33:44.042209Z 0 [ERROR] [MY-010257] [Server] Do you already have another mysqld server running on port: 3306 ?
2021-03-23T07:33:44.042744Z 0 [ERROR] [MY-010119] [Server] Aborting

This means that there is likely another instance of mysqld running, and that's why it was not possible to start it again.

Overall, your system seems to be in an inconsistent and/or problematic state based on the outputs I analyzed from the logs. If possible, it would be helpful to have more logs for e.g. the following operations:

# apt purge mysql-server-8.0
# apt install mysql-server-8.0

Since it seems likely to me that this is a local configuration problem,
rather than a bug in Ubuntu, I am marking this bug as 'Incomplete'.

However, if you believe that this is really a bug in Ubuntu, then we would
be grateful if you would provide a more complete description of the problem
with steps to reproduce, explain why you believe this is a bug in Ubuntu
rather than a problem specific to your system, and then change the bug
status back to "New".

For local configuration issues, you can find assistance here:
http://www.ubuntu.com/support/community

[Expired for mysql-8.0 (Ubuntu) because there has been no activity for 60 days.]