LONDON — After being closed for 163 days by the coronavirus pandemic, the British Museum on Thursday became the last of Europe’s major museums to welcome back visitors.

As at other institutions these days, there were hand sanitizer stations and one-way routes, a limited number of visitors, and many masks. But the museum has made some more permanent changes, too.

Hartwig Fischer, the museum’s director, said in an interview that the killing of George Floyd by Minneapolis police in May, and the subsequent Black Lives Matter protests around the world had “altered the awareness of everybody.” The events made him want to intensify the museum’s work addressing its links with slavery and colonialism, he said.

The museum made two main changes for the reopening, Mr. Fischer said. The first was moving a bust of Hans Sloane — a physician and collector of curiosities whose holdings formed the basis of the museum when it was founded in 1753 — from a plinth in a prominent gallery to a display case. Now Sloane is no longer simply celebrated as a natural history collector, but labeled a “slave owner.” The vitrine contains other objects related to Britain’s involvement in the slave trade.

This week it was mostly social conservatives who criticized the museum, but in June it was rebuked by social justice advocates when it issued a statement in support of Black Lives Matter demonstrations. In the statement, Mr. Fischer said the British Museum was “aligned with the spirit and soul” of the movement. That idea was widely mocked online.

“Did our lives matter when your STOLE ALL OUR THINGS?” Stephanie Yeboah, an author, wrote on Twitter. “If we matter that much to you, give it back.”

The lack of diversity among the museum’s senior curatorial staff also came into the spotlight in June, when a BBC interviewer asked Mr. Fischer how many of the museum’s 150 curators were Black. He said none were, adding that it was a “big issue we need to address.” (He was actually wrong, a spokeswoman for the museum said: The museum has one Black curator, an archaeologist.)

Mr. Fischer said the museum had been trying to address its links to colonialism and slavery since before he joined, in 2016, by researching the origins of items in the collection to work out how they had been acquired, and involving communities associated with the artifacts in curatorial decisions. The new text that explains Hans Sloane’s links with slavery had been “co-written with the Black British community,” for example, he said.

“It’s not a beginning when it comes to facing our own history,” Mr. Fischer said, adding, “You’ll see much more of this in the future.”

For years, the museum has faced calls to return key items from the collection to their countries of origin, including the Benin Bronzes, a dazzling collection of hundreds of artifacts taken by British forces in a brutal 1897 military raid. The treasures are now scattered in museums and private collections around the world. The British Museum has said it would loan some of the items to Nigeria when it builds a new museum to display them, but has resisted calls to return them permanently.

Some supporters of the British Museum say it can’t win in this climate. “The British Museum is the kid at school that everybody’s decided to mess with and bully,” said Bonnie Greer, a Chicago-born playwright and journalist, in an email. Ms. Greer, who is African-American, was the deputy chair of the museum’s board for four years and hosted a series of talks there earlier this year about how cultural institutions can reckon with colonialism’s legacy.

“They do a lot and should talk about it,” she said. The fact the museum doesn’t blow its own horn, she added, was likely “a British thing.”

Maria Morte, 50, said she had read about the bust in a newspaper. “Doing this, it’s very with the times, isn’t it?” she said.

“I think it’s a good decision,” she added. “Before it just said about his travels and how his great collection came about. But the legacy of slavery, you can’t ignore.”