WiFi / WLAN, mwave ovens, bluetooth and a lot of other things use the 2.4 GHz ISM-band which has 100 MHz BW centered at 2.45 GHz (ISM = Industry, Scientific and Medical). Thus mwave ovens are said to use 2.45 GHz but is is probably whatever in that band, most likely centered at 2.45 GHz but BW varies.
WiFi has also got other frequency allocations, most know are the 5 (and recently 6) GHz bands. Older audio equipment use to only use 2.4 GHz which unfortunately is very crowded. WiFi has also allocations ~60 GHz, we will burn that bridge when we arrive.
It is wellknown since decades that mwave ovens may interfere with other users in the 2.4 GHz ISM band. As OP report, one can try to use a fixed channel, preferably at the borders of the 2.4 GHz band. If it is possible to move to 5 GHz that is much better for many reasons.
Are then these mwave ovens a health hazards? In most cases not! Restorer may of course ditch his oven, question is just what qualities the next oven will have -- mwave leakage is unaviodable in equipment like these consumer products with a mwave generator marked as ~1 kW (rated power). RF power decreases fast with distance, geometrically it goes as ~1/r**2, path loss in the air further reduces the rf field strength. Health safety limits have varied over time, al have been set with a considerable margin. - I wouldn't worry.