None of the chargers I have used require disconnecting the battery, at all.  Best to read and follow the unit manufacturers instructions for your application.

no sir/ma'am

i have a cheapo from walmart, works fine

I have a car I don't drive much and have used a Battery Minder brand tender on it for years. As others have said, you don't have to disconnect the battery to use it.

If you're around to start the car once every week or two, personally I'd leave out the charger & just disconnect the negative terminal, but be sure to get the engine up to operating temp & then run it above 2000-2500rpm for a good 15-20 mins to burn off any corrosive garbage settling inside the engine.

Even if it's stationary you're alright but it's best to also run in through the gears as well. I had to do this since October as it only just got warm enough for me to replace the brake lines. In my case I removed both terminals however & experienced no loss even with the subzero temps. Trick was to keep an eye on the weather & made sure I ran it the day prior to a cold snap.

Letting it just sit for extended periods will eventually lead to rust/pitting if the various byproducts aren't burned off. This can take months (or years) depending on where you live but in high humidity environments it comes on fast unless you fog the engine prior to storage.

I've been using these on farm equipment, motorcycles and cars for many years, and they work great with a trickle charger. You connect them to the battery and leave the connector out the grille or the like, and just plug them into the trickle charger. That way, there's much less fuss. Many trickle chargers come with them.

https://www.amazon.com/Terminal-Connecters-Extension-Connector-Maintainer/dp/B079ZTBHYK/ref=sr_1_3?keywords=12+Connector+for+Battery+Charger+Ring+Terminal&qid=1648911858&sr=8-3