Make sure you have the utilsplugin2 plugin installed in JOSM.
Go to the utilsplugin2 settings, and review the entries
The first four entries are default, the others are examples of custom entries you can add. Now add the following entries, which are helpful alternatives to their plugin counteparts:
For Mapillary, use the URK: "https://www.mapillary.com/app/?lat={#lat}&lng={#lon}&z=19&focus=map"
For Bing Streetside, use the URL: "https://www.bing.com/maps?cp={#lat}~{#lon}&lvl=17&lvl=19.7&v=2&sV=1&style=x"