I guess I'm an on-again-off-again learner of Ainu. I first started learning it in 2015 while I was preparing to get interviewed for a Russian
ALT position at a school in Nemuro, Hokkaido. I wasn't really expecting it to be useful there, but I had always been interested in learning about Ainu, and I thought that living in Hokkaido provided the perfect excuse to do so. In the end I didn't get the job, but I stuck with that year's STV course until the end, after which I gradually let it slip away. I did get the urge to pick it back up again at some points afterwards but, being focused on other languages, I've mostly managed to keep my wanderlust at bay. However, most recently I was inspired to refresh my knowledge of Ainu by this year's anime adaptation of the manga Golden Kamuy, which also inspired me to try my hand at
tweetiing in Ainu.
Another good resource that's available in English (in addition to Japanese) is the
Topical Dictionary of Conversational Ainu, a dictionary consisting of topic-based modules of words and sentences, complete with audio recordings by a native speaker of the Saru dialect. It doesn't really give a detailed introduction to the grammar though, so if you feel like that would be necessary you might want to use it as a supplement to a full course. The 2006 translated STV course is based on the Shizunai dialect, which is geographically right next to Saru, but I'm not sure to what extent they are actually similar. The Saru dialect appears to be the one studied the most, since for a long time it had the largest number of surviving native speakers, including those in
the largest remaining Ainu-majority community. I also remember hearing that the Chitose dialect is about as popular, likely due to its traditional area's proximity to Sapporo (while Hokkaido's largest city is located in the subprefecture called
Ishikari, what's known as the Ishikari dialect was actually spoken further up the Ishikari river, around the inland city of Asahikawa).
Speaking of the dialects, the Foundation for Research and Promotion of Ainu Culture has
several multi-level courses for various Ainu dialects (in Japanese only). While the STV course I completed previously was based on the Ishikari dialect, if I ever go back to seriously studying Ainu I was thinking of doing the Saru dialect course and supplementing it with the Topical Dictionary. No idea when I'll actually do it though, as right now I'm trying to focus on Biblical Hebrew and Setswana. But then, trying to get a boost in Ainu in time for the start of the second season of Golden Kamuy in October does sound like an interesting side challenge...
Edit: the link to the Saru dialect beginner level textbook PDF on the website erroneously leads to the Tokachi dialect one instead, but
the file does exist under the correct URL.