You'll have to fix the collation manually as the error says to do. Your table collation is completely wrong for a Joomla install (utf8mb4_0900_ai_ci) and should be utf8mb4_unicode_ci. You can use phpMyAdmin and the Operations tab tool to fix collation for all tables and their columns. I will try to add an additional installer fix for this, but I can't guarantee that'll work.

Try running all the database fix tools in CB > Tools, starting with "Check Community Builder Database" and working your way down. If there's any errors, they'll be red, they'll have a fix link. Click that fix link to fix any database issues. Then retry install. If still not working you'll need to wait for a new build release tomorrow where I'll try adding additional fixes for databases with collation problems like yours. The alternative is you can try contacting your host to see if they'll fix the database collation for all tables and their columns to utf8mb4_unicode_ci.

I do not have any further solutions for you at this time then outlined above. Will review further improving the installer to account for additional collation issues tomorrow, but your database has a completely wrong collation for a Joomla install and will be a problem as time goes on.

The only real way to fix that is as instructed above. Your hosting panel should have software called phpMyAdmin. Login to that and click your database on the left in the sidebar. From there click the Operations tab at the very top. Now scroll down to the "Collation" section and in the dropdown select utf8mb4_unicode_ci. Now click the "Change all tables collations" checkbox followed by the "Change all tables columns collations" checkbox. Once that's done click the "Go" button bottom right of the "Collation" section. That should fix your table collations once and for all.