The strike letter has a list of activities that are "officially" part of the strike:
These include both raising and handling flags, closing/deleting posts, and handling review queue tasks.
They do not include asking/answering, commenting, or voting up/down.
Personally, I've also stopped answering and all voting (might have slipped and voted here and there; also I have not stopped activity on Meta sites) and restricted my comments to an occasional handful. Some moderators around the network are still doing most of those things, others are avoiding use of the site completely. One of your elected moderators here at Academia.SE has resigned entirely. There is a userscript for "read-only" mode that some people are using:
There is no "enforcement" of the strike like a typical paid labor action might involve, we're volunteers on the site and we're volunteers in the strike. Everyone can participate to the extent they feel is most useful, and some participants may feel certain actions are too important to avoid.
Most importantly, the strike does not involve only moderators, but also curators and any other users of the site that want to participate. As of now, 121 moderators, 19 former staff and former moderators, and 1251 regular users have signed on to the strike. The best action to take for people who support the strike is to sign the strike letter. The next best action I would take would be to spend some time to become an "informed citizen", there are some useful links at the meta post mentioned in the question:
Academia.SE Moderation Strike
There's an update post on Meta (though this has now also aged a bit):
Moderation Strike update: Data dumps, choosing representatives, GPT data, and where we’re holding
Former employee and moderator Jon Ericson has a blog that has recently focused at lot on the strike and associated issues, he has a very interesting perspective as a former insider:
There's the announcement and then retraction of the Stack Overflow "formatting assistant", released during the strike, that feeds questions into ChatGPT with a prompt asking to format them as if they were written by someone who knows how to write SO questions. The results are...interesting...and not surprisingly hit on many of the issues strike participants previously expressed about GenAI:
In addition, there is a main meta post related to the question asked here:
Would the striking moderators welcome a user strike? Should we, the users, go on strike?