No need to apologise, a polite "I ran X which solves Y" related to the post is encouraged. Helps the rest of us learn about other solutions out there :-)
I've found that candidates have little or non appetite for take home problems.
If they are busy interviewing, putting aside 2-3 hours (which is not much really) per interview, limits how many they are willing to do per week. As its still a candidate driven market.
Keep in mind, people have to find the spare time while doing their jobs and living life. If they have a family - good luck finding spare time :-)
The best win/win I've found is to pair with someone for about 30 minutes. You help each other, just like you do in real life.
so what would the experience be for someone new joining the project, particular if you have many repositories? having to search across numerous repositories? In practice I've found this (source control commit messages as ADR's) doesn't work. Unless I have mistaken what you have said? I just keep a repository for ADR's, which can then be published to a wiki or else where.