Comment 2 for bug 1923010

Thanks for your report and your help to make Ubuntu better.

From you log this seems to be a real crash:

2021-04-07T17:09:57.616740Z 0 [ERROR] [FATAL] InnoDB: Table flags are 0 in the data dictionary but the flags in file ./ibdata1 are 0x4800!
2021-04-07 19:09:57 0x7f053ee22740 InnoDB: Assertion failure in thread 139660506572608 in file ut0ut.cc line 916
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.7/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
17:09:57 UTC - mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
Attempting to collect some information that could help diagnose the problem.
As this is a crash and something is definitely wrong, the information
collection process might fail.

key_buffer_size=16777216
read_buffer_size=131072
max_used_connections=0
max_threads=151
thread_count=0
connection_count=0
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 76385 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0 thread_stack 0x30000
/usr/sbin/mysqld(my_print_stacktrace+0x3b)[0x55a2a8de48eb]
/usr/sbin/mysqld(handle_fatal_signal+0x489)[0x55a2a86dd679]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x153c0)[0x7f053f3983c0]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0xcb)[0x7f053ee8a18b]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x12b)[0x7f053ee69859]
/usr/sbin/mysqld(+0x61d9b9)[0x55a2a86b39b9]
/usr/sbin/mysqld(_ZN2ib5fatalD1Ev+0x145)[0x55a2a8fbd0a5]
/usr/sbin/mysqld(+0xfd80ab)[0x55a2a906e0ab]
/usr/sbin/mysqld(+0xfd8717)[0x55a2a906e717]
/usr/sbin/mysqld(_Z6fil_ioRK9IORequestbRK9page_id_tRK11page_size_tmmPvS8_+0x2e8)[0x55a2a9077cc8]
/usr/sbin/mysqld(_Z13buf_read_pageRK9page_id_tRK11page_size_t+0xdd)[0x55a2a902ab6d]
/usr/sbin/mysqld(_Z16buf_page_get_genRK9page_id_tRK11page_size_tmP11buf_block_tmPKcmP5mtr_tb+0x4ca)[0x55a2a8ff8efa]
/usr/sbin/mysqld(_Z31trx_rseg_get_n_undo_tablespacesPm+0x152)[0x55a2a8f9a462]
/usr/sbin/mysqld(+0x61cb3d)[0x55a2a86b2b3d]
/usr/sbin/mysqld(_Z34innobase_start_or_create_for_mysqlv+0x2f5d)[0x55a2a8f6622d]
/usr/sbin/mysqld(+0xd9786a)[0x55a2a8e2d86a]
/usr/sbin/mysqld(_Z24ha_initialize_handlertonP13st_plugin_int+0x4f)[0x55a2a872ad9f]
/usr/sbin/mysqld(+0xb321d5)[0x55a2a8bc81d5]
/usr/sbin/mysqld(_Z11plugin_initPiPPci+0x600)[0x55a2a8bcf9d0]
/usr/sbin/mysqld(+0x63fa2f)[0x55a2a86d5a2f]
/usr/sbin/mysqld(_Z11mysqld_mainiPPc+0x810)[0x55a2a86d7190]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0x7f053ee6b0b3]
/usr/sbin/mysqld(_start+0x2a)[0x55a2a86cda2a]

Further from your logs it seems that this is a fresh mysql install - is that correct?
I wonder where it should get bad table data then - is on that system an old DB that might not work well with the new server?

Checking the internet for this kind of errors I've found that the most likely case seems to be a database that was created/used with a new mysql e.g. 8.0 and then trying to use an old mysql e.g. 5.7 with it.

In your logs I then found:

Start-Date: 2021-04-07 16:32:40
Commandline: apt-get install mysql-server
Requested-By: bigdata (1000)
...
Start-Date: 2021-04-07 18:32:01
Commandline: apt-get install mysql-server-5.7

So you installed "mysql-server" which in Ubuntu 20.04 is mysql-8.0.
So far so good, that should be fine and work.

But later on you installed 5.7 from some other (non supported) source.
And this crashes.

You need to
a) use the mysql-8.0 from the archive as that is what the DB files on disk match
b) fully purge the package and the database, then re-install the 5.7 server - but be aware that this is not supported it isn't in the Ubuntu repository of 20.04 and therefore will not get fixes and security updates.

I'll mark this incomplete as it seems a local configuration issue, more than a bug in Ubuntu.
If you think it is a package bug please explain why and re-open the case.