The inability to save images from the mobile app without screenshotting (talk about a perverse incentive) is one of the reasons I hate IG
I stumbled upon this userscript which adds the view image button back, seems to work so far https://gist.github.com/ner00/ec9ae47e202b8e99f19be44a5af6ba...
I don't use ig,tiktok, snap but people around me do and its very annoying.
Instagram has on by default unless you touch to mute it.
Facebook has audio on by default.
Don't know about tiktok. Its banned in India for past 3-4 years
I asked around.