paulwpxp

Also, it’s worth noting that this could be just a caching problem. I’d clear/purge all the caches related to the site.

Thanks for getting back to explain more in details. I now understand what you meant. You were right about the concern regarding old and new content, there will be problems down the road.

I thought that if the Classic Editor plugin is only going to be supported until 2022, then maybe there is going to be a time limit on the Classic Block as well.

If that ever happens I can only hope that’d be after the Convert to Block functionality is superb!

This is the support forum for the theme you are using
https://wordpress.org/support/theme/smartline-lite

So the site is using a pretty old version of the theme and old version of WP. I would definitely create a staging site and test it before doing this kind of update to the live site. Also remember to have a full site backup, most webhost providers have this thing usually called one-click backup.

So the scan results show this

Known javascript malware: rogueads.unwanted_ads?1

Malware Found
{your site url}/404javascript.js

Malware Found
{your site url}/ru/home/ 

Did you try to login via FTP or cPanel to delete those files?

Also make sure you update your security plugins, or try different one.

Update your theme, and make sure all plugins are updated without security issues.

Contact your hosting provider, letting them know the issue, it might get injected from other site hosting on the same box.

Now I can’t see your site, there is error “too many redirects” going on. I guess this is the “but now nothing will load.” mentioned in your first post.

This page contains info for “too many redirects” error and how to fix it.
https://kinsta.com/blog/err_too_many_redirects/

Have you tried clearing browser’s cache/history? Your site front page is looking just fine on my end. There is a slideshow and a search bar down below, right?

Is there any reason–like future-proofing, for example–to convert all older pages and posts to blocks using Convert to Blocks?

Generally, it’s not necessary to convert old posts to Block.
https://github.com/WordPress/gutenberg/issues/12694#issuecomment-445458488

and if you need to do it, there is no reason to be rush. Your old content will always be there safe and sound. At the moment, not many people use Convert to Block option just yet so we don’t know much about its performance in all different situations. Depending on the type of content, doing it now you might encounter some problems that give you headache. Better wait for more improved, and more stable version.

I’d rather do it now than a few years down the line when there are even more posts…

That’s not true. Only new posts will be in Blocks, the amount of old format (Classic Block) will be the same not more.

Yes, purge database cache, db cache is the first suspect for the error you have.