I had to do a domain change on a website so I moved from www.mydomain.it to www.mydomain.eu. At the moment I don't have full control on the .it domain so when it was the time to make the domain change I asked the hosting provider to make a 301 redirect of the .it to the .eu so as a result, I got all the pages of the .it website redirected to my .eu's homepage (no 404 errors) because the previous website used queries as pages' URLs.
This is a link example of the previous website:
http://www.mydomain.it/index.php?page=lkr_pg_chisiamo
So what I started getting after the redirect was:
https://www.mydomain.eu/index.php?page=lkr_pg_chisiamo
which gave me back the homepage content as a result and not a 404 error.
The old website had at least 10k links like that one so each of them started having the behavior of the link above, I got the homepage content for all links. In the beginning, I thought it was a good thing for me because I wasn't getting 404 errors but then I started digging around on the web and I found out to not be a good practice because all links might be recognized as soft 404 errors.
Obviously before I made the domain change I had created all the 301 redirects of the most important pages of the website like this:
RewriteCond %{QUERY_STRING} ^page=lkr_pg_chisiamo$
RewriteRule ^(.*)$ https://www.mydomain.eu/chi-siamo/? [R=301,L]
RewriteCond %{QUERY_STRING} ^page=lkr_pg_contattaci&form_key=25-8124355$
RewriteRule ^(.*)$ https://www.mydomain.eu/contatti/? [R=301,L]
And so on..
Obviously, I didn't do that for all the 10k pages, but just the most important, so the other links are still pointing to the homepage content.
After I did this, I told Google I had changed the domain through the Google Search Console.
After a few weeks, I started seeing some results on Google but after one month I'm not still happy with them, I think I lost rank on Google. I know it could take a while more to do everything and that I should probably lose 3% of my "domain juice" after a domain change but what I was wondering if I have done everything in the right way in order to not lose rank.
My concern now is about all the links that I wasn't able to redirect and that has been redirected automatically and started getting the homepage content. Should I be worried about them?
How should I manage them?
Should I redirect them to another page which is not the homepage?
If yes, is there a way to redirect all those links (just those) even though I have all the other redirects in my .htaccess file?
Was there a better way to redirect all the 10k links of that type? How would I be able to do that?
