The vast vast majority of the population is still heterosexual.
It can be hard to be a minority or to go against the grain. Pretty scary as there is still a lot of anti LGBTQ+ feelings out there and a ton of scare mongering.
I’m actually surprised there isn’t a larger Queer element on this forum but maybe not. Perhaps people know of more specific forums that might have more help?
Love and support is the most important thing as always. Hopefully you have a strong open relationship and you can learn together. Good luck to you both.
Firstly I’d advise fuck Tommy Robinson and any of his ilk.
Secondly, it’s fine to be whatever you/your teen are. People don’t fit in to pigeonholes, I’ve got friends who are now identifying as a different gender that I knew them as originally, and friends who I know did a lot of same sex things during their youth but are now married to someone of the opposite gender, and lots more between. Then I remember one of my friends pulled a card during Cards Against Humanity, which said “heteronormativity” and didn’t know what it meant. Another friend pointed at me and said “basically this guy!”, which is fine to be. I think whatever your sexuality, being comfortable in it is the main thing
As for “material” similar to things like Nuts and Zoo, I guess there’s a reason it died off. I’m sure there are sites that have “softcore” material instead of +18 photos/videos. It is probably also worth a conversation with them (as they’ll undoubtedly view some kind of porn at some point in their life) to say that what they see in porn isn’t real. These are paid actors, and even with “amateur” videos/images, it’s not a true reflection of a relationship most of the time.
Having a child that came out as gay - the only thing I can tell you is just make sure they know they are loved. Make you sure tell them you love them, there is nothing “wrong” with them and you are proud of them.
There’s tons of advice regarding gender identity on the internet and it’s relatively easy to shy away from the darker side of the internet. Searching terms like the transition steps how to seek advice will bring up pages and pages of information. Also help from a GP is worth looking into, as this will help to gain HRT and counselling. Counselling isn’t necessarily to advise your teen to change their views, it’s more in place to see if they’re 100% sure that they’re making the right decision.
There’s loads of influencers on TikTok and FB these days who share their transitional journey, it maybe worth searching some of these influencers and they’ll explain the process more thoroughly.
Don’t let narrow minded politicians, media and individuals drag you or your teen down. Sadly this is the community we live in these days and there’ll always be someone who will give a sly remark. It’s not only the LGBTQ community that have to deal with these type of people, it’s the same for people who have disabilities, nationality. It’s a cruel world unfortunately.
The best thing you can do is support your teen, and let them be themselves, and be the person they want to be. Your love and support will be plenty to help guide them on the path they want to lead.
I think any teen is gonna be completely mortified to have their parent give them the talk about stuff sexual but at same time letting them know they can come to you about anything with not hesitation or anxiety is equally important… sometimes sharing your own teen experiences can help them to feel more at ease to open up… but ultimately when it comes to porn and sexual content, sadly it’s an inevitable thing they will likely come across or seek out to explore from curiosity which is totally natural as we all have done it in our youth.
As long as they know how to be safe and treat others with respect then that’s the main tools you can hope to arm them with in this era.
Hopefully you have a strong open relationship and you can learn together. Good luck to you both. 
