I think in the younger generations most people are OK with transgenderism in general, the GRA and 'transwomen are women'. I'm in that generation and this is where i was until recently.
Mostly because they haven't thought about it too much.
Partly because in our generation there is a drive to be as progressive and inclusive as possible, which is a good thing but misguided in this case.
And majorly because it only recently started to become a real problem.
The odd post-transition transwoman identifying as female and playing on a womans team really isn't a big deal a lot of the time. In a small community people tend to know eachother, transpeople get a certain notoriety, and it's is possible to be pretty sure that that transwoman is safe to share female spaces with so most people are comfortable with that.
However the Trans Rights Movement has gained so much ground in such a short time that most people (feminists, trans people, and the general public) mistakenly believes that that's still where the conversation and situation is at. Considering how hard and publicly women and minorities have had to fight for the smallest gains it's truly shocking how quickly and silently these vast changes have been brought in.
So when TRAs tell them that TERFS are against trans rights, they think we're still talking about Passing Paula being allowed to come and hang out in the ladies loos at the pub. They don't realise we're talking about Creepy Carl having the LEGAL RIGHT to declare that his dick is female and every one who disagrees is committing a hate crime.
Also, transgenderism is based on sexism, which is still fundamental to the way our society works and the way our whole thought processes are structured. Even if you don't AGREE that dolls are for girls and trucks are for boys, you still KNOW that idea and you have known it since before you could talk. So it's been very easy for Trans Rights to slip in to those same sexist slots while pretending it's about protecting poor disadvantaged people.
TO answer your question, based on my personal friend circle it's about 0% of feminists (and just regular women) over the age of 45 who are ok with the GRA.
It's about 85% of LGBTQ groups who are supportive of it, even if they otherwise agree that male violence is a problem and men pretending to be women shouldn't be in womens spaces, it seems to me they're sort of in the habit of defending and including people who claim to be excluded and disadvantaged.
It's about 50% of the general public under 45 years old accept it. Many of them are swayed with 5 minutes of discussion just showing the harm that is already happening due to it.