I was about to post this! According to this analysis in Ukraine there are up to 273 thousand men aged 25 and 26 who could be summoned. This figure excludes students, who are exempt at any age, but includes men of this age who are already serving as contract soldiers.
Moreover, regarding students, the possibility for male college students between the age of 18 and 22 to spend a study period of up to 6 months abroad was approved - upon invitation from the host foreign university and upon possession of a document from the local Territorial Recruitment Center. I think the limit is 22 because it shouldn’t be ruled out that in the second half of this year or in 2025, the minimum mobilization age may be lowered to 22, as many officers are asking for. That said, I found out just a few weeks ago, however, that for guys who have not turned 21 yet there is a need for parental consent to sign a contract.
As for the mobilization law, last week the Defense Committee of the Verkhovna Rada finished discussing and voting on the 4269 (!) amendments. By mid-April, more or less, the law will go to the parliament for the second reading and we will finally know the final details.