Many old posts with links to Wikipedia articles contain http rather than https links. As far as I can tell, it is better to have https link rather than http. (After all, internal links have been changed in such way: Network-wide HTTPS: It's time.)1
And there are also many posts which contain a link to mobile Wikipedia. To my knowledge, it is better to have a link to the full site - on mobile devices the mobile version will be displayed anyway, and the users on desktops don't have to change the version.2
In both cases, there was some manual editing of such links. (I have noticed such edits on some sites that I frequent. I have included at least some stats below at least for this site.)
I was told that CMs have at their disposal some tools which can bulk replace links - and such things have been done in the past.3
Question 1. Would it be useful (and possible) to convert such links in bulk - at least on bigger sites? (I suppose that larger sites are likely to have more such posts than what is suitable for manual editing.)
Question 2. Would changing http to https be an option for some domains which are common on some site - after a list of such domains would be compiled on meta? (For example, I could imagine things like converting http://doi.org/ to https://doi.org/ or http://arxiv.org to https://arxiv.org on sites which often link to scientific articles.)
1Let us take this site as an example. I got 2433 results from search and 2469 results from SEDE. There might be about 75 instances of edits where http was changed to https for a Wikipedia link. On Stack Overflow I get about 240k results from search. (And the queries linked above will time out for SO.)
2On Meta Stack Exchange I get 41 results from search and 43 results from SEDE. In this case I found only 8 such edits. Searching on SO returns about 3k results.
3One of the CMs pointed out to me some examples when such thing was done in the past: Is it possible to mass-update broken URLs to IndianScriptures.com with HinduScriptures.in?, Chakoteya.net links are broken, chabadlibrary.org link structure has changed, and there are now many broken links. There is also this example on Meta Stack Exchange: Links to HTML versions of RFC's need to move from "tools" to "datatracker". See also: How to find and/or change a set of hyperlinks on a site?
secure.wikimedia.org, which was the way to access Wikipedia via HTTPS before it was implemented on the main Wikipedia domain.en.m.wikipedia.orgmight be necessary to help in getting across what the OP is trying to show. But I would expect this to be less likely on sites unrelated to IT (for example, MathOverflow). Re: this is not a one-time effort. That's certainly true for the mobile site. But I would expect that now people will include only https links to Wikipedia (since that's what they get when they visit Wikipedia). So at least the http to https conversion would be done only once.