bad mouth taste on day 10. starting flu and throat itchiness. is it linked with keto

It can be quite normal to experience all these things within the first couple of weeks of a Keto lifestyle, while your body is getting to use this carb restriction.  Sore throat, flu-like symptoms will usually disappear within a few weeks.  In the meantime, be sure to drink lots of water, up your electrolytes and try and drink bone broth.  Those 3 things really helped me through the first few weeks of keto.  Many times the bad mouth taste will go away, people who get often say it almost has a metallic taste?  Again, increase your water and hopefully, that too will pass as your body adjusts to its new macros.  Good luck and although you feel under the weather now, it won't last and you'll come out of it feeling better than you've ever had before.