Good question. Firstly you do not have to be flexible to practice yoga. Worth repeating YOU DO NOT HAVE TO BE FLEXIBLE TO PRACTICE YOGA. Neither do you need to be fit, if you can breath you can practice yoga.
I would recommend finding a local class. The advantage of going to a class is the teacher will aid and advise you with getting the poses correct, not hurting yourself, and making modifications to a pose if required. Put your postcode into google followed by "yoga class" see what comes up. Sometimes you'll find classes in a church hall, school or local park.
Yes there are many types, you may want to try a few classes if possible to see what suits you. Many people start with traditional "Hatha" classes. But it depends what's available locally. At the end of the day it's all yoga.
If class is not a option, youtube has many beginners videos. I understand "yoga with Adriene" is very popular. Another online is a step by step intro to Ashtanga yoga here
https://onyouryogamat.com/lay13/
I've been very lucky to find two good local teachers who are very helpful and don't mind answering my many questions. When I started it was (and still can be!) difficult. My first ever class we sat crossed legged for five minutes doing breathing exercises, but I couldn't sit cross legged as it hurt so much. Now I sit cross legged with my bum on a block. Childs pose hurt my legs, should be a resting pose! Now I use a block to place my head on in childs pose. Seated forward fold I couldn't reach my toes, now I use a strap around my feet. In fact I can reach my toes now, but not always, after three years of regular practice. After that first class the teacher asked my how it went, I explained I couldn't do it. She said that was good, then you will enjoy learning, see you next time. She was right.