These are the gold standard for heating a fastener while minimising damaging to the surroundings, except if there are delicate electronics nearby. The downside is, they are VERY expensive. Consider this option only if you are a pro or very active DIYer... or loaded!

Draper Expert 1750W Induction Heater Tool Kit | Handheld Portable Quad Coil Induction Heater | Garage Workshops | 80808
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1100W Magnetic Induction Heater Kit, 220V Flameless Handheld Bolt Heater with 3 Coils, Bolt Removal Tool, Rusty Screws Removing Tool, Electromagnetic...
4.0

1500W Electric Magnetic Induction Heater Tool Kit with 4 Coil, Portable Hand‑held Screw Bolt Heat Extractor for Rusty Screw Removing, Nut Buster