let us see opinions of sunni scholars

ibn hajar quotes in his tehzeeb under heading

[801] د ت س أبي داود والترمذي والنسائي بسر بن أرطاة

then he writes the opinion of darqutni about him, who said

وقال الدارقطني له صحبة ولم يكن له استقامة بعد النبي

he had suhbat (that means he was sahabi/companion of prophet) but he did not had integrity after holy prophet

he further writes

وسمعت يحيى يقول كان بسر بن أرطأة رجل سوء

yahya said that basr bin artaat was a bad man

keep in mind that ahmad bin hanbal made a chapter for him in his musnad

مسند أحمد » مسند الشاميين » حديث بسر بن أرطاة رضي الله تعالى عنه

most important, however, is the saying of darqutni, who accepts that he was a sahabi, and did not show integrity later on
which for sure means, just becoming sahabi is not enough ……………………