While typing hashtags on #Mastodon you can see how many posted recently (997 for exampel in Mastodon)
At least on desktop try typing:
#Mastodon (shows 997 post)
#tech 330 posts

Notice sometimes it will show it will not show you the posts for predictive text tags BUT if you do type it fully it will show you
like #technology shows 38 posts but typing #technolo doesn't show it until fully typing the word...
enjoy #freeschool (<----- 0 per week!)