The executors are talking rubbish. It is their responsibility and theirs alone to progress matters and they cannot use use solicitors, estate agents, state agencies or other delays for their lack of progress.
They need to come up with a list of assets to be liquidated (property, cash, other holdings) and a list of creditors to be paid (funeral costs, other bills, insurances, etc.). Upon accepting their appointment as executors they took on the responsibility to protect the estate for the beneficiaries and to distribute the proceeds as per the wishes expressed in the will in a timely and efficient manner. If they cannot fulfil these requirements it is up to the beneficiaries to replace them, a legal process and potentially costly.
If a sibling is willing to purchase the house, the price to them is the open market valuation less their share of the asset as stated in the will. e.g. market valuation is €240,000 house split 4 ways, the sibling purchasing it pays (€240,000 - €60,000) plus their own conveyancing & inspection costs (engineer, solicitor, taxes, duties, etc.) It is a regular house-purchase transaction apart from the discount.