For commercial users of LT, you could suggest a minimum donation (monthly or yearly) for each user in an organization.
For developers of products that use LT, you could suggest a minimum donation for each sale (possibly as a percentage of the sale value).
(Page https://languagetool.org/donate/ shows expenses as 50 euros. The correct value is more than 600 euros. I suggest that you also add a list of things that you would like to do, but which will cost money.)