Hi,
I did some testing too. As a temp workaround, you can enclose the p tags of the paragraph in block editor comments. This work when you have both editors enabled (classic and block in settings > writing). They will then remain in the both editors (because WP fires a javascript version of autop which has that). In the Falang editor they will also copy these encapsulating comments, but (since that is MCE and does not use that javascript but MCE settings) there the p tags will replaced with an empty line, so you can still recognise the paragraph in text view, but the comments from the block editor remain.
So if you enter in text mode classic:
<!-- wp:paragraph -->
<p>
Your paragraph goes here.
</p>
<!-- /wp:paragraph -->
Then the p tags remain visible in text view after saving and after switching to visual and back and saving. It seems the new autop has been set up to respect those comments in the Classic Editor too.
In Falang MCE translation this shows as (after save):
<!-- wp:paragraph -->
Your paragraph goes here.
<!-- /wp:paragraph -->
so without the p tags showing, but with a blank line in place of the p tags. This then translates fine in the frontend, as before. When no tag is specified for a block of text, that block will automatically get wrapped inside a p tag in the frontend (by autop).
Maybe that helps for now?