CEX like Binance is probably easiest - Buy ATOM or OSMO, then withdraw and buy TIA on Osmosis.

If you have used Thorchain, then avoiding a CEX is possible - deposit HIVE onto tribaldex, swap to LTC or BNB or something. Withdraw to a wallet connected to Thorchain, swap whatever you had to ATOM - go to Osmosis and swap to TIA.

I so badly wish HIVE had some proper bridges.

Actually, I just checked, and TIA is on some decent exchanges, so maybe the CEX option will work best. Important to withdraw and stake your TIA natively - use Keplr wallet or Leap.