Honestly, I would be cautious. As you know, Giardia is contagious, and best practice is to isolate an infected dog from others.
Heffalump came to us with Giardia, by the time we figured out what was going on my other dogs picked it up as well. With a pack living together cycles of re-infection were a real risk, so we had to isolate, confining the dogs to my garden and each in a separate room in the house.
Daily bathing, and daily laundry washed on the hottest cycle - fun times.
Have you spoken to your vet about isolation? What does he/she recommend?
So - you need to figure out how to give your pup the socialization necessary for his development stage, while maintaining safety for all.
Are you signed up for a Welpenforderung class? Obviously your pup should not be in a class right now, especially with other puppies, but the trainer could be a big help to you nonetheless.
If so, ask the trainer for ideas on socialization opportunities to replace the normal contact a puppy should have at this age.
And more important: ask the trainer to help you make a plan for post-isolation remedial socialization, so that you are on top of the ‘catching up’ your pup will need to do.
During the pandemic lockdown, some trainers offered Zoom classes. Ask yours if something similar might be possible, if only just to keep you in the loop with usual developmental stage issues.
Use this time for age-appropriate interactive learning games at home. Work on naming games, search games, age-appropriate skills development, clicker training, etc. Bring different sounds, textures, smells into the home, let your puppy get used to these.
(Time to link my favorite at-home brain training game resource again, Spass Mit Hunde. You’ll need to calibrate the games you make for your puppy’s age, but there are lots of good suggestions. Games made of normal household objects will help acclimate your pup to new things, new textures, new experiences, too.
https://www.spass-mit-hund.de
If the vet agrees, perhaps you could take your pup out in a pouch carrier, so that you could see and hear other people and animals an environmental sounds without direct contact or without touching the ground. The pup would still be learning about the environment. Go to a variety of places, where the pup would see and hear different thigns going on around him.
A word of caution: everybody love a puppy, people will try to pet yours without asking. Be ready to stop them, saying that your pup is in medical isolation. The carrier will help, but some people are just clueless.
Give your pup a bath just before going out. And wash that carrier pouch daily!
How is the house training going? As you know, feces are a source of transmission. Obviously staying on top of hygene is critical - and it must be all the more difficult with a puppy so young that control is not yet possible. Do you have a place for your pup to urinate/deficate that is yours exclusively, not shared with anyone - human or animal? If not, you might have to resort to paper training at home. I usually advise against that, as it really is just doubling the work - but if you are in a shared space that might be necessary.
The silver lining is that you can probably get a good jump on learning not only basic house training, but also the oh-so-important-when-you-have-a-train-to-catch skill of piddling on command.
I really feel for you and your pup. Hopefully this will be a one-and-done for you, and that you can get your pup back into society in 4-6 weeks.
But please do call on your vet and trainer for more advise.
Wishing you both all the best.