The Latin-Romanian sound correspondences exclude any possibility for the Romanian iubi 'to love' to be a descendant of the Latin iubeō (iubēre, iussī, iussum) 'command, order'.
Latin ē/oe and i became Romanian /e/:
Front vowels changed as follows:
• ē/oe and i became /e/.
• ī became /i/.
• /ɛ/ in stressed syllables
• /e/ in unstressed syllables
Subsequent to this, stressed /ɛ/ diphthongized to /je/.
Lat. pellem > *pɛlle > Rom. piele /pjele/ ('skin')
Lat. signum > *semnu > Rom. semn ('sign')
Lat. vīnum > *vinu > Rom. vin ('wine')
Note, different Latin vowels became Romanian /e/ or /ɛ/, but there are no instances of Latin e/ē becoming Romanian /i/.
What do we see in our words iubeō (iubēre, iussī, iussum) and iubi? The Latin verb is of the 2nd declension, that is the -ē- declension. In the 1st p. sg. present iubeō the -ē- is shortened before another vowel (o), in the active infinitive iubēre it is long as it should be. Also, it is long in other forms whenever it is possible.
On the other hand, the Romanian verb belongs to the -i declension and we see that i in all the forms of the verb whenever it is possible (the personal suffixes -esc, -ești, and -ește are added only to the verbs in -i most of which correspond to the Latin verbs with infinitives in -īre). The verbal noun from iubi is iubire.
The final -i in a Romanian infinitive can develop only from i, Romanian i cannot appear from an older e, this means iubi cannot be a descendant of the Latin iubeō, the best candidate for the source of iubi is the Slavic lubiti which has the stem lubi- in all the Slavic languages.