Hi
Sounds good... the whole J3 to j4 must be a nightmare :)
Not that bad, 4SEO is actually designed to be independant from Joomla as much as can be, so that differences between J3 and J4 can be isolated to specific, simple parts where I can easily spot issues.
So once the problem is identified, and the root cause known, it's not had to fix.
But yes, generally speaking, it's hard not so much because if Joomla but also because many extensions also behaves or are programmed differently under J3 and J4, so extensions such as 4SEO which work/support many other extensions basically have twice the work.
Hopefully that will pay off and users will be able to transition from one to the other...
Best regards
Yannick Gaultier
weeblr.com / @weeblr