The 25-year-old has moved to Boston United from Guiseley after two seasons with the Lions, following Ben Pollock into the Jakemans Community Stadium.
The former Tadcaster Albion, Sheffield FC, Ossett United and Goole player has been an impressive performer for Guiseley, despite their relegation from the National League North on the final game of last season.
Mbeka, who is known for his physical presence and ability to find the net, fits in with Paul Cox's style of bringing in players he deems 'hungry' to succeed.
"Lebrun is another player that we have been monitoring over the last two seasons,” Cox told bufc.co.uk.
"His performances have been consistently impressive during that period and he has fulfilled a variety of roles within the team during that time.
"We are taking on a player with huge potential and I am looking forward to working with Lebrun once pre-season gets under way."
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