ooofree I also had an issue with wikimedia/less.php as you seem to be having. I tried to upgrade it to version 3.0 with Composer directly but the Flarum plugin was blocking it. What ended up working for me was removing it using composer remove. From there I was able to upgrade Flarum. After I upgraded Flarum what happened is that it re-installed wikimedia/less.php to the proper version (v3.0) that it wouldn't let me install before, haha.
