The point of this list is to collect my favorite tomboy content (with limited ecchi). What follows is a very brief case for each title, in the order of my rating. Obviously these span lots of varieties of tomboy. No spoilers beyond the first chapters.
Fujiyama's Adolescence (9) - Coming of age, sporty/tall tomboy, chapter 1 start of the relationship, completed, and beautiful.
12cm Promise with a Cool Girl (9) - Coming of age, sporty/tall tomboy, ongoing, great character design and development.
Aoi-kun Wants This Muscular Girl to Flex! (8.5) - Adult romance, muscular tomboy, 14 chapters and complete. Subverts bad tomboy tropes (yay!)
Fighter Saotome, Cover Up (8.5) - This is top tomboy boxing coming of age, it's complete and it's great. They get together in chapter 1 in a hilarious way.
How to Treat a Lady Knight Right (8) - Fantasy setting, lots of abs, comedy. Fairly long, complete.
Men's Life: Her Secret Life in the Boys' Dormitory (8) - Crossdressing/sporty tomboy coming of age first romance story. 15 chapters and complete. Kind of absurd premise, but if you get over that it's a fun read.
Tomo-chan is a Girl! (8) - Classic completed tomboy manga with a great anime adaptation.
Don't Toy With Me, Miss Nagatoro! (8) - Sporty but also feminine tomboy (is that an oxymoron? am I an oxymoron?) that builds the romance over time. Great anime adaptation. Completed.
Boyish Girlfriend (8) - Coming of age, starts with dating firmly established but also takes some time for the romance to develop. Solid tomboy FMC. Ongoing.
Ouran High School Host Club (8) - Classic completed cross-dressing tomboy with a great anime adaptation. This one is out there but it's great. First released in 2001.
Hitomi-chan is Shy With Strangers (7.5) - Tall tomboy coming of age - you have to overcome the MC's terrible haircut. Completed.
My New Girlfriend is Not Human? (7.5) - Supernatural, short chapters, pretty heartwarming.
The Muscle Girl Next Door (7.5) - Short, completed, and completely described by the title! Cute and worth it.
Childhood Friend Complex (7.5) - College tall/sporty/male presenting tomboy. This one had some interesting things to say about gender roles but kind of fumbled a little in my opinion towards the end. Still good. Complete.
A Big Rabbit Has Taken a Liking to Me!? (7) - This was a bit borderline for me, and is relatively new. I'm not a fan of the extreme smoking, but otherwise it's kind of fun. I will likely revise this as it (hopefully!) gets more chapters.