June is a great time to visit that area. I have never heard of anyone bass fishing the harbor in Sheboygan. There are probably some bass there but not worth your time targeting.
Sheboygan is only about an hour south of Sturgeon Bay in Door County. Door county has some of the best smallie fishing in the country. June is a good time to visit. Depending on what time In June you will be visiting and how quickly the water will warm up will dictate the fishing. It’s looking to be a warm spring so they will likely be post spawn.
Sturgeon bay is the southern most bay and warms up quicker than the bays further north. All the bays hold bass and can be great depending on conditions.
Techniques are mostly finesse - tubes, Ned rigs, drop shot, wacky, paddle tails, jerk baits, etc. Use natural color and floro line. Super clear water. Hiring a guide is probably the right call to get you up to speed quickly.
Fishing can be tricky and requires some patience. The reward can be some great number days with legit chances at multiple 5 lb fish. Pay attention to weather as conditions it can get nasty in a hurry. Just use caution. Also make sure your boat is has all the coast guard requirements.
If you go, you can stop at Howie’s bait shop in Sturgeon bay. They can point you in the right direction and offer some tips. It’s a beautiful area as well. Good luck!